Very bad engine knock!

[Zeik75]

Hi everyone i have a problem with the 88 Bonne, she has the LN3 engine with 166xxx miles on it with no major engine work at all but it seems my luck has ran out. Alright pretty bad problem here i started hearing the sounds just today but i have felt a different kind of shake for about a week now, this morning as i was going to school when i put it in gear it would make like a thud sound and feel like it was running rough like bad plugs but when i got going and rpms held at about 2000 it would feel fine. throughout the day (leaving school, going to work, ect...) it got progressively worse until when it starts there is a knock and when put in gear there is a bad engine knock. i think the sound is still there when in park but unless you know about it and are in the engine bay you cant tell. had my dad come look at it when i got home and he is 90 percent the lifters have finally died.

if i can figure out what the problem we can pull the engine ourselves and rebuild it if needed i suppose but i more want to just keep it running well because i was planning on an engine swap this summer but if it must be rebuilt ill just do that and keep this engine until i have money to blow.

if anyone can give me ideas or confirm whats wrong it would be just the biggest help. i have a video of the sound that i will try and post also to help.

[J Wikoff]

You might rule out the harmonic balancer. Can you grab the belt and move it along its path? If you take the belt off and run it for several seconds, does the sound change?

[MattStrike]

If you put your head under the car, listen ot the oil pan. If it's rod knock, you will know, it will be very loud.

Also, another easy trick is to pull the dipstic and hold it up to sunlight and look for sparkles. If metal is in the oil, then it's most likely rod knock. Lifters make a tapping/clacking noise when they are bad, and don't *normally* leave sparkles in the oil.

[Zeik75]

Thanks guys ill check those when i get home from school today and get back to ya.

[olblueeyesbonne]

95 out of 100 of these 1990-older 3800's get scrapped simply b/c a harmonic balancer is shot and whoever diagnosed the problem diagnosed it wrong, thinking it was a main or rod bearing.

In other words, my vote is that the harmonic balancer is bad. $25 or less from a salvage yard and shouldn't take 1 hr to change or under $40 for a shop to do it.

[Zeik75]

sorry i haven't gotten back earlier. I've done some inspecting, tried a couple things to fix lifters if they were sticking but that didn't do anything. So finally i pulled off the oil pan tonight and found some bad things.

this was all in the bottom of my oil pan, the little chunks are some really hard plastic. if anyone knows what they broke off of, or where the spring came from.
Also we noticed all 6 piston rods could be wiggled and moved back and forth on the crankshaft bearing.




sorry not the best pics but i couldn't find my camera so i just used my ipod.
It seems like one of the two endcaps i took off had some very slight scoring on it on one edge, thats the one that had the scoring on it, cant really see it in the pic though.
I also have a video with the sounds while its running but im not sure how i should put videos on here...

[bill buttermore]

It is normal for the connecting rods to move or slide side to side. The question is: Do any of them move up and down against the crank journal? That is what you will find if the problem is a worn rod bearing causing a knock. That bearing shell in your hand looks pretty good for 166K. Crank journal looks pretty good, too.

You might want to carefully and cleanly put the bearing back and button up the pan. Check torque spec.s for the rod bolts.

Have you checked out the harmonic balancer yet? That would have been my first guess like the others have advised you.

[myfirstbonnie]

That spring looks like it is from the timing chain tensioner.

[rustyroger]

X2 on the tensioner, I have been advised it's a good idea to chage the whole timing gear assembly around 100k miles.

Hopefully you might get away with it.

A bad harmonic balancer wouldn't cause bits to appear in the oil pan, however it will have to come off anyway so replacing with a new one might be a good idea.

Roger.

[MattStrike]

X2 not a bearing problem. If the crank journals look polished, and there isn't any sparkly in the oil then bearing are good. If a bearing went bad, the journal would look like it got sandpapered or ridged (like a rotor that wore metal to metal) and the oil would be sparkly like metallic paint. If you're in doubt, get some plasti-gage for the scored journal. If it's on the high side of tolerance then replace that bearing, but I don't see a problem. Definately clean out the oil passages in the pump/filter/sump that you can reach, something had to get in the oil to score the journal.

X3 on gunk being from timing chain/tensioner.

Put the video up on youtube and link to it.

[Zeik75]

Alright thanks guys ill get the video up tonight and ill go ahead and get a new harmonic balancer. But os it possible to change the timing chain with it in the car?

[bill buttermore]

Alright thanks guys ill get the video up tonight and ill go ahead and get a new harmonic balancer. But os it possible to change the timing chain with it in the car?

Yes.

[MattStrike]

You will need to get a harmonic balancer puller, and some bolts to fit the balancer - I can't remember it they're 1/4-28 or 6x1.25 or whatever thread, but need about 3" long. Most HB puller kits don't have them.

Is the old balancer actually bad then?

[J Wikoff]

If you checked all the rod bearings, I suspect your noise is coming from the untensioned timing chain. Maybe the balancer is still bad though. Check to see if the outer hub has rotational play around the middle, and for a circular crack in the rubber running out near the outer hub.

[Zeik75]

alright i got the video uploaded on youtube http://youtu.be/ELJi6rgHYj8.

Im not sure if the harmonic balancer is bad yet didn't have a chance to work on it today. also can i not just reuse the balancer bolts, and for that matter the bolts on the piston rods too? i know with some bolts such as the cam bolt you aren't supposed to reuse it but i'm not sure how many different things that applies to.

[bill buttermore]

alright i got the video uploaded on youtube http://youtu.be/ELJi6rgHYj8.

Im not sure if the harmonic balancer is bad yet didn't have a chance to work on it today. also can i not just reuse the balancer bolts, and for that matter the bolts on the piston rods too? i know with some bolts such as the cam bolt you aren't supposed to reuse it but i'm not sure how many different things that applies to.

In this thread:

viewtopic.php?f=20&t=2497

the procedure is given for re-using connecting rod bolts in a '91 H-body. You should be able to re-use the big bolt on the HB, and in some of the older 3800s, the HB was not press-fit. No puller was required - they just slid off. Maybe yours will too. If not, the procedure is given for HB removal in Techinfo.

[crash93ssei]

That sound in that video is no rod knock like I have ever heard, that sounds like your timing chain is slapping around.

100% sure those bits you found in your oil pan is parts of your timing chain tensioner, that is the only thing in the engine with hard plastic and a spring like that.

Many years ago, before I found this site I had an '89 SE Bonneville and I had a mechanic friend of mine replace the timing chain for me and I vividly remember the spring looking just like that. Don't run that engine anymore, remove the harmonic balancer, all the accessories off the front (belt side) of the engine, the timing cover and replace your timing gears, chain, and tensioner. Be absolutely sure to thoroughly check the timing cover for any wear from the chain to be sure you don't need to source another cover. A little wear into it will not be an issue, but if it is wore deep you may want to look into replacement.

*EDIT*
Be careful when reinstalling the harmonic balancer and crankshaft position sensor. The sensor is adjustable and can slide around in and out and if not set properly the teeth on the interrupter ring on the balancer will tear the sensor apart.

[MattStrike]

I can't say I've ever heard a 3.8 make that noise before.

It's not rod knock or HB. Get the timing chain and damper replaced for sure

[myfirstbonnie]

Also remember these had the spring and button holding the cam in the block. With the tensioner spring in the pan, I am wondering if the button is gone or very weak and allowing the cam to walk. You need to pull the front cover and inspect the cover for wear and the timing set. If you find the button is bad, you may have damaged the cam bearings.

Time for a good inspection.

[Jrs3800]

Pull the front cover.... The chain and tensioner are way way done...